330191-00-08-90-CN | Bently Nevada 3300 XL 8 mm Probe, 9.0 m

What Is the 330191-00-08-90-CN Proximity Probe?

The 330191-00-08-90-CN is a Bently Nevada 3300 XL 8 mm eddy current proximity probe engineered for precise, non-contact displacement and vibration measurement on rotating machinery. Specifically, this model features a 3/8-24 UNF thread and is supplied without armor, making it suitable for installations where a flexible, unarmored probe cable path is preferred. With a total length of 9.0 meters (29.5 feet), the probe supports long cable runs between the machine casing and the associated transducer driver. The 8 mm probe tip provides a thicker encapsulation of the probe coil in molded PPS plastic, resulting in a more rugged sensor. Furthermore, the larger probe body diameter delivers a stronger, more robust case. Consequently, Bently Nevada recommends 8 mm probes whenever possible for optimal robustness against physical abuse.

Key Specifications of the 330191-00-08-90-CN

• Input Voltage: Requires -17.5 Vdc to -26 Vdc when installed with a nonincendive circuit per installation drawing 140979.
• Output Current: 12 mA maximum consumption; -23 Vdc to -26 Vdc with barriers.
• Isolation: Not isolated; operation at a more positive voltage than -23.5 Vdc can result in reduced linear range.
• Sensitivity: Less than 2 mV change in output voltage per volt change in input voltage.
• Output Resistance: 50 Ω.
• Nominal Probe DC Resistance: 9.87 ± 0.50 Ω from center conductor to outer conductor.
• Probe Tip Material: Polyphenylene sulfide (PPS).
• Probe Case Material: AISI 303 or 304 stainless steel.
• Cable Type: 75 Ω triaxial, FEP insulated.
• Tensile Strength: 330 N (75 lbf) probe case to probe lead; 270 N (60 lbf) at probe lead to extension cable connectors.
• Connector Material: Gold-plated brass or gold-plated beryllium copper.
• Maximum Connector Torque: 0.565 N·m (5 in·lbf).
• Probe Case Thread: 3/8-24 UNF, maximum thread engagement 0.563 in.
• Weight: 323 g/m (11.4 oz).
• Temperature Range: -55°C to +232°C (probe only, depending on EPL classification).

For specifications not listed here, refer to the official Bently Nevada datasheet.

Failure Mode Analysis: Why Precision Matters

In rotating machinery protection, a proximity probe failure can lead to false trips or, worse, undetected machine damage. The 330191-00-08-90-CN addresses common failure modes through several design features. First, the patented TipLoc molding method provides a robust bond between the probe tip and body, reducing the risk of tip separation under vibration. Second, the CableLoc design delivers 330 N (75 lbf) pull strength, preventing cable detachment. Third, the 8 mm probe's thicker PPS encapsulation protects the coil from physical abuse. Additionally, the Viton O-ring seals differential pressure between the tip and case. However, note that probes are not pressure tested prior to shipment. For reliable operation, always respect the specified input voltage range; operating at a more positive voltage than -23.5 Vdc reduces linear range and may cause inaccurate readings. By understanding these failure modes, engineers can specify the 330191-00-08-90-CN with confidence for critical applications.

Installation and Compatibility

The 330191-00-08-90-CN is designed for use with Bently Nevada extension cables and Proximity Transducer Drivers (Prox). The probe entity parameters are met when used with BN extension cables and connected to BN Prox. For one-meter systems, no extension cable is used; however, this 9.0-meter probe requires an extension cable to reach the driver. The 3/8-24 UNF thread ensures secure mounting. When installing, observe the maximum connector torque of 0.565 N·m (5 in·lbf) to avoid damage. The unarmored cable provides flexibility but requires protection from mechanical abrasion. The CN agency approval option indicates country-specific approval; verify compliance with local regulations. For integration into plant control systems, the probe output is a voltage signal proportional to shaft displacement. Ensure the associated Prox driver matches the probe's 9.0-meter length for proper calibration.